Fluctuating internal pressures induce fatigue stresses in pipes and fittings. The influence of these fatigue loadings on the strength of unplasticized polyvinyl chloride (UPVC) and polyethylene (PE) pipe systems is examined. The fatigue response of UPVC pipe is well defined. For PE pipe systems elevated temperature fatigue tests identify fittings and joints as the prefered failure sites. The literature indicates that PE pipe systems, jointed by butt fusion in particular, have the best projected fatigue lifetimes, and are capable of withstanding significant surge fatigue stressing at 20/23°C.